Image forming apparatus that determines color misregistration amount

Abstract

An image forming apparatus includes: a control unit configured to form, onto an image carrier, a detection pattern including a first image group including a plurality of first images and a second image group including a plurality of second images, and determine a color misregistration amount in a rotational direction and a width direction orthogonal to the rotational direction based on a detection result of the detection pattern. The detection pattern includes a plurality of basic patterns arranged at a first interval in the rotational direction, and each of the plurality of basic patterns includes the first image group and the second image group arranged at a second interval in the rotational direction, and the first image group and the second image group arranged at a third interval different from the second interval in the rotational direction.

What is claimed is: 
     
         1 . An image forming apparatus comprising:
 a plurality of photoreceptors that are rotationally driven and on which images of different colors are formed;   an image carrier that is rotationally driven and to which images formed on the plurality of photoreceptors are transferred;   a detection unit configured to detect an image transferred to the image carrier; and   a control unit configured to form, onto the image carrier, a detection pattern including a first image group including a plurality of first images of different colors and a second image group including a plurality of second images of different colors by forming a first image and a second image on each of the plurality of photoreceptors to transfer the first image and the second image to the image carrier, and determine a color misregistration amount in a rotational direction of the image carrier and a color misregistration amount in a width direction orthogonal to the rotational direction based on a detection result of the detection pattern by the detection unit, wherein   the first image is a linear image in a first direction different from the rotational direction,   the second image is a linear image in a second direction different from the rotational direction and the first direction,   the detection pattern includes a plurality of basic patterns arranged at a first interval in the rotational direction, and   each of the plurality of basic patterns includes the first image group and the second image group arranged at a second interval in the rotational direction, and the first image group and the second image group arranged at a third interval different from the second interval in the rotational direction.   
     
     
         2 . The image forming apparatus according to  claim 1 , wherein the control unit uses a detection result by the detection unit of the first image group and the second image group arranged at the second interval in order to determine a color misregistration amount in the rotational direction, and uses a detection result by the detection unit of the first image group and the second image group arranged at the third interval in order to determine a color misregistration amount in the width direction. 
     
     
         3 . The image forming apparatus according to  claim 1 , wherein the first image group in the first image group and the second image group arranged at the second interval is same as the first image group in the first image group and the second image group arranged at the third interval. 
     
     
         4 . The image forming apparatus according to  claim 1 , wherein the first image group and the second image group arranged at the second interval are different from the first image group and the second image group, respectively, arranged at the third interval. 
     
     
         5 . The image forming apparatus according to  claim 1 , wherein
 the plurality of basic patterns are N basic patterns that are integers of 2 or more, and   the first interval, the second interval, and the third interval are intervals based on N.   
     
     
         6 . The image forming apparatus according to  claim 5 , wherein the first interval corresponds to a distance moved by a surface of the image carrier during a period {S+ (1/N)} times a rotation period of the plurality of photoreceptors or a motor that drives the plurality of photoreceptors, and S is an integer of 0 or more. 
     
     
         7 . The image forming apparatus according to  claim 5 , wherein
 the second interval corresponds to a distance moved by a surface of the image carrier during a period an odd multiple of (½N) times a rotation period of the plurality of photoreceptors or a motor that drives the plurality of photoreceptors, and   the third interval corresponds to a distance moved by a surface of the image carrier moves during a period an even multiple of (½N) times the rotation period.   
     
     
         8 . The image forming apparatus according to  claim 5 , wherein the first interval is an interval corresponding to a phase difference of 2π/N, when a distance moved by a surface of the image carrier during a period in which the plurality of photoreceptors or a motor that drives the plurality of photoreceptors makes one rotation is one period. 
     
     
         9 . The image forming apparatus according to  claim 5 , wherein
 the second interval is an interval at which the first image group and the second image group have opposite phases, when a distance moved by a surface of the image carrier during a period in which the plurality of photoreceptors or a motor that drives the plurality of photoreceptors makes one rotation is one period, and   the third interval is an interval at which the first image group and the second image group are in phase, when a distance moved by a surface of the image carrier during a period in which the plurality of photoreceptors or a motor that drives the plurality of photoreceptors makes one rotation is one period.